In previous experiments, we have found that excitation of the nucleus pontis oralis yields masseteric reflex facilitation and excitatory postsynaptic potentials in masseter motoneurons during wakefulness and quiet sleep, whereas during active sleep there arises reflex inhibition and inhibitory postsynaptic potentials. These responses are independent of the intensity of stimulation; they are dictated solely by and are completely dependent on the animals's state. Thus, a single reticular site can induce different patterns of somatomotor control according to the behavioral state of the animal. We have called this paradoxical phenomenon "reticular response-reversal." The research described in this application is designed to clarify the pathways and neuronal circuitry underlying the differential state-dependent modulation of somatic activity exerted by the reticular core of the brainstem. Interdisciplinary electrophysiological studies are proposed, each of which relates to and complements the others. These studies, which are to be undertaken during wakefulness, quiet sleep and active sleep, entail an examination of the state-dependent activity of, and interrelationships between, neurons of the nucleus pontis oralis, the nucleus reticularis gigantocellularis and the trigeminal motor nucleus. We propose to employ our new technique of intracellular recording in the chronic cat as well as correlated spike-triggered averaging to explore patterns of reticular activity and interaction. Our experiments are designed to provide basic data relating to the brainstem control of motor processes, while at the same time they are organized within the framework of a hypothesis which we have proposed to explain the phenomenon of reticular response-reversal.